Many personal care products currently available to consumers are directed primarily to improving the health and/or physical appearance of the skin. Among these skin care products, many are directed to delaying, minimizing or even eliminating skin wrinkling and other histological changes typically associated with the aging of skin or environmental damage to human skin.
Skin is subject to insults by many extrinsic and intrinsic factors. Extrinsic factors include ultraviolet radiation (e.g., from sun exposure), environmental pollution, wind, heat, low humidity, harsh surfactants, abrasives, and the like. Intrinsic factors include chronological aging and other biochemical changes from within the skin. Whether extrinsic or intrinsic, these factors result in visible signs of skin aging and environmental damage, such as wrinkling and other forms of roughness (including increased pore size, flaking and skin lines), and other histological changes associated with skin aging or damage. To many people, skin wrinkles are a reminder of the disappearance of youth. As a result, the elimination of wrinkles has become a booming business in youth-conscious societies. Treatments range from cosmetic creams and moisturizers to various forms of cosmetic surgery.
Extrinsic or intrinsic factors may result in the thinning and general degradation of the skin. For example, as the skin naturally ages, there is a reduction in the cells and blood vessels that supply the skin. There is also a flattening of the dermal-epidermal junction which results in weaker mechanical resistance of this junction. See, for example, Oikarinen, "The Aging of Skin: Chronoaging Versus Photoaging," Photodermatol. Photoimmunol. Photomed., vol. 7, pp. 3-4, 1990, which is incorporated by reference herein in its entirety.
Vitamin B.sub.3 compounds, particularly niacinamide, have recently been found to provide measurable skin regulating benefits. For example, topical niacinamide helps to regulate the signs of skin aging, i.e., reduce or efface the visibility of the fine lines, wrinkles, and other forms of uneven or rough surface texture associated with aged or photodamaged skin. These compounds have also been found useful in reducing the overall oiliness of skin.
In formulating products containing vitamin B.sub.3 compounds, much attention is directed toward providing compositions which deliver and retain optimal concentrations of the vitamin B.sub.3 compounds in the stratum corneum with minimum absorption into the systemic circulation. Furthermore, promoting user compliance with respect to chronic treatment regimens is also important. Current vitamin B.sub.3 formulations, however, can be drying and irritating. Such formulations may cause individuals to refrain from using vitamin B.sub.3 products as frequently and copiously as is necessary for optimum benefit.
The present inventors have found that compositions containing natural or synthetic vitamin B.sub.3 compounds along with a preservative component comprising a formaldehyde donating preservative and a halopropynyl compound, deliver the skin regulating benefits of a vitamin B.sub.3 compound with reduced dryness and/or irritation. These compositions have improved user acceptance and, thus, promote better user compliance with a concomitant overall improvement in skin regulating benefit.
It is, therefore, an object of the present invention is to provide natural or synthetic vitamin B.sub.3 containing skin care compositions having improved skin compatibility.
Another object of the present invention is to provide natural or synthetic vitamin B.sub.3 compositions containing preservative systems which provide preservation activity at concentrations of no more than 0.2%.
Still another object of the present invention is to provide natural or synthetic vitamin B.sub.3 compositions containing preservative systems which do not substantially impact niacinamide stability or bioavailability.
These and other objects of this invention will become apparent in light of the following disclosure.